1. Field of the Invention
This invention relates generally to methods of forming metallurgy on semiconductor integrated circuits and more particularly to a process for forming such metallurgy using a single layer of photoresist in which both negative and positive images can be developed to allow all the metallurgy needed on the device to be defined using the single layer of photoresist. 2. Description of the Prior Art
The application of lithography in the manufacture of integrated circuits is well known to the art. Generally speaking such lithographic processes, as practiced in the semiconductor art, include deposition of a layer of photoresist material on the surface of the body. The photoresist material usually comprises a polymer with additives therein. The coated body can be then exposed to electromagnetic radiation, such as, for example light, electron beams, etc., in order to change the solubility of the exposed portions of the photoresist layer. The layer is then developed with selective solvents which remove the soluble portions of the layer and uncover surface areas on the surface of the body. To form different portions of the final metallurgy that is desired on the surface of the body using the prior art multiple resist layers are deposited, patterned, exposed and developed and removed. With each layer defining a different pattern or portion of the final metallurgy necessitates that each such layer of resist and pattern to be carefully aligned with respect to the previously processed layers and patterns. As device become smaller alignment problems, using multiple layers of resist, increase resulting in a yield decrease.